diff options
Diffstat (limited to 'locks/os2/thread_rwlock.c')
| -rw-r--r-- | locks/os2/thread_rwlock.c | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/locks/os2/thread_rwlock.c b/locks/os2/thread_rwlock.c new file mode 100644 index 0000000..195a56b --- /dev/null +++ b/locks/os2/thread_rwlock.c @@ -0,0 +1,200 @@ +/* Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#include "apr_general.h" +#include "apr_lib.h" +#include "apr_strings.h" +#include "apr_portable.h" +#include "apr_arch_thread_rwlock.h" +#include "apr_arch_file_io.h" +#include <string.h> + +static apr_status_t thread_rwlock_cleanup(void *therwlock) +{ + apr_thread_rwlock_t *rwlock = therwlock; + return apr_thread_rwlock_destroy(rwlock); +} + + + +APR_DECLARE(apr_status_t) apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock, + apr_pool_t *pool) +{ + apr_thread_rwlock_t *new_rwlock; + ULONG rc; + + new_rwlock = (apr_thread_rwlock_t *)apr_palloc(pool, sizeof(apr_thread_rwlock_t)); + new_rwlock->pool = pool; + new_rwlock->readers = 0; + + rc = DosCreateMutexSem(NULL, &(new_rwlock->write_lock), 0, FALSE); + + if (rc) + return APR_FROM_OS_ERROR(rc); + + rc = DosCreateEventSem(NULL, &(new_rwlock->read_done), 0, FALSE); + + if (rc) + return APR_FROM_OS_ERROR(rc); + + *rwlock = new_rwlock; + + if (!rc) + apr_pool_cleanup_register(pool, new_rwlock, thread_rwlock_cleanup, + apr_pool_cleanup_null); + + return APR_FROM_OS_ERROR(rc); +} + + + +APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock) +{ + ULONG rc, posts; + + rc = DosRequestMutexSem(rwlock->write_lock, SEM_INDEFINITE_WAIT); + + if (rc) + return APR_FROM_OS_ERROR(rc); + + /* We've successfully acquired the writer mutex so we can't be locked + * for write which means it's ok to add a reader lock. The writer mutex + * doubles as race condition protection for the readers counter. + */ + rwlock->readers++; + DosResetEventSem(rwlock->read_done, &posts); + rc = DosReleaseMutexSem(rwlock->write_lock); + return APR_FROM_OS_ERROR(rc); +} + + + +APR_DECLARE(apr_status_t) apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock) +{ + /* As above but with different wait time */ + ULONG rc, posts; + + rc = DosRequestMutexSem(rwlock->write_lock, SEM_IMMEDIATE_RETURN); + + if (rc) + return APR_FROM_OS_ERROR(rc); + + rwlock->readers++; + DosResetEventSem(rwlock->read_done, &posts); + rc = DosReleaseMutexSem(rwlock->write_lock); + return APR_FROM_OS_ERROR(rc); +} + + + +APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock) +{ + ULONG rc; + + rc = DosRequestMutexSem(rwlock->write_lock, SEM_INDEFINITE_WAIT); + + if (rc) + return APR_FROM_OS_ERROR(rc); + + /* We've got the writer lock but we have to wait for all readers to + * unlock before it's ok to use it + */ + + if (rwlock->readers) { + rc = DosWaitEventSem(rwlock->read_done, SEM_INDEFINITE_WAIT); + + if (rc) + DosReleaseMutexSem(rwlock->write_lock); + } + + return APR_FROM_OS_ERROR(rc); +} + + + +APR_DECLARE(apr_status_t) apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock) +{ + ULONG rc; + + rc = DosRequestMutexSem(rwlock->write_lock, SEM_IMMEDIATE_RETURN); + + if (rc) + return APR_FROM_OS_ERROR(rc); + + /* We've got the writer lock but we have to wait for all readers to + * unlock before it's ok to use it + */ + + if (rwlock->readers) { + /* There are readers active, give up */ + DosReleaseMutexSem(rwlock->write_lock); + rc = ERROR_TIMEOUT; + } + + return APR_FROM_OS_ERROR(rc); +} + + + +APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock) +{ + ULONG rc; + + /* First, guess that we're unlocking a writer */ + rc = DosReleaseMutexSem(rwlock->write_lock); + + if (rc == ERROR_NOT_OWNER) { + /* Nope, we must have a read lock */ + if (rwlock->readers) { + DosEnterCritSec(); + rwlock->readers--; + + if (rwlock->readers == 0) { + DosPostEventSem(rwlock->read_done); + } + + DosExitCritSec(); + rc = 0; + } + } + + return APR_FROM_OS_ERROR(rc); +} + + + +APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock) +{ + ULONG rc; + + if (rwlock->write_lock == 0) + return APR_SUCCESS; + + while (DosReleaseMutexSem(rwlock->write_lock) == 0); + + rc = DosCloseMutexSem(rwlock->write_lock); + + if (!rc) { + rwlock->write_lock = 0; + DosCloseEventSem(rwlock->read_done); + return APR_SUCCESS; + } + + return APR_FROM_OS_ERROR(rc); +} + +APR_POOL_IMPLEMENT_ACCESSOR(thread_rwlock) + |